Heat exchanger, especially for motor vehicle, and method for producing such a heat exchanger

ABSTRACT

The invention relates to a heat exchanger, notably for a motor vehicle, said exchanger comprising a core bundle for the exchange of heat between a first and a second fluid, said core bundle comprising a plurality of tubes ( 3 ) and a header tank ( 2 ), said tubes ( 3 ) and said tank ( 2 ) allowing said first fluid to circulate between them, said exchanger further comprising a retaining plate ( 16 ) for holding said tubes ( 3 ), said plate ( 16 ) being fixed to said tank ( 2 ), said tank ( 2 ) comprising a collector plate ( 6 ) provided with orifices through which said tubes ( 3 ) pass, said collector plate ( 6 ) being made of plastic. 
     The invention also relates to a method of manufacturing such an exchanger.

The present invention relates to a heat exchanger and to a method ofmanufacturing such an exchanger. It is particularly aimed atapplications in the automotive vehicle field, notably as a radiator forcooling the heat-transfer fluid used to cool the engine of the vehicles.

In automotive applications there are two known main types of heatexchanger: a first type, referred to as mechanical, corresponding toexchangers which are obtained by assembling their components by thedeformation of material, and exchangers referred to as brazedexchangers, corresponding to exchangers obtained by assembling theircomponents using brazing.

Mechanical exchangers are made up mainly of a core bundle of tubesthrough which a heat-transfer fluid circulates and of a plurality offins arranged perpendicular to the tubes and provided with orificesthrough which said tubes pass. The purpose of the fins is to increasethe surface area for exchange with the air passing through theexchanger. An exchange of heat between the fluid circulating through thetubes and the air passing between the fins is thus obtained.

The fins are held on the tubes and the tubes are held on the collectorplates by expanding the tubes. More specifically, an expansion olive ispassed along the tubes, inside same. It has the effect of deforming thematerial of the tubes thereby increasing their cross section and thusallows the tubes to be kept pressed against the fins.

One benefit of mechanical exchangers over brazed exchangers is theirgreat ease of assembly. Specifically, brazed exchangers require brazingovens which involve significant investment, whereas mechanicalexchangers can be produced with installations that require far lowerinvestment.

Nevertheless, in mechanical exchangers, the collector plate and thetubes are made of metal and therefore subject to corrosion. Such aphenomenon is further amplified by a galvanic effect between thecollector plate and the tubes. Corrosion weakens the tubes and/or thecollector plate and introduces a risk as to the fluidtightness of theexchanger.

To alleviate this disadvantage, header tanks made of plastic havealready been proposed. These are tubular in shape and provided withorifices for the passage of the tubes. However, with such a solution itis difficult to expand the tubes given the amount of space availableinside the tank. Immobilizing the tubes with respect to the tankstherefore presents problems.

The present invention seeks to overcome these disadvantages and relatesfirst of all to a heat exchanger, notably for a motor vehicle, saidexchanger comprising a core bundle for the exchange of heat between afirst and a second fluid, said core bundle comprising a plurality oftubes and a header tank, said tubes and said tank allowing said firstfluid to circulate between them, said exchanger further comprising aretaining plate for holding said tubes, said plate being fixed to saidtank, said tank comprising a collector plate provided with orificesthrough which said tubes pass, said collector plate being made ofplastic.

Because the collector plate is made of plastic, the corrosion phenomenaencountered with the metal collector plates of the prior art areavoided. In addition, by attaching the tubes to the tank via theretaining plate, the problem of immobilizing the tubes relative to thetanks is solved.

According to various embodiments which may be considered together orseparately:

-   -   said retaining plate is attached externally to said tank,    -   said retaining plate is attached to said collector plate,    -   said tank comprises a cover, attached to said collector plate,    -   said cover is made of plastic,    -   said cover and said collector plate are fixed by welding,    -   said tubes are made of metal,    -   said tubes are made of aluminum alloy,    -   said exchanger further comprises a gasket through which said        tubes pass,    -   said gasket is situated outside said header tank,    -   said gasket is compressed between said tubes and said collector        plate at an outline of said orifices provided in said collector        plate for the passage of said tubes,    -   said tubes are flared at their ends,    -   said flare extends at least facing said retaining plate and/or        said collector plate, or even facing said gasket,    -   said retaining plate is removable with respect to said header        tank.

The invention also relates to a method of manufacturing such anexchanger, said method comprising:

-   -   a step of fixing said tubes to said retaining plate,    -   a step of attaching said retaining plate to said header tank.

According to various embodiments of the invention which may beconsidered together or separately:

-   -   said step of fixing the tubes in the retaining plate involves a        step of flaring said tubes in said retaining plate,    -   said method comprises a step of introducing said tubes into said        collector plate,    -   said step of introducing the tubes into said collector plate is        after the step of fixing said tubes to said retaining plate        and/or before the step of attaching said retaining plate to said        header tank,    -   said step of introducing said tubes into said collector plate        comprises a step of force-fitting said tubes into said collector        plate and/or said gasket.

The attached figures will make it easy to understand how the inventionmay be embodied. In these figures, references that are identical denoteelements that are similar.

FIG. 1 is an elevation schematically illustrating an exchanger accordingto the invention.

FIG. 2 is an exploded perspective view of a header tank of a heatexchanger according to the invention.

FIG. 3 is a partial perspective view of a core bundle of a heatexchanger according to the invention.

FIG. 4 is a perspective view showing the mounting of the core bundle ofFIG. 3 on the header tank of FIG. 2.

FIG. 5 is a perspective view showing one example of a heat exchangeraccording to the invention, after assembly.

FIG. 6 is a perspective view showing an alternative form of embodiment,according to the invention, of the exchanger of FIG. 5.

As illustrated in FIG. 1, the invention relates to a heat exchanger 1exchanging heat between a first and a second fluid. This is an exchangerof the mechanical type. It comprises a core bundle of tubes 3 throughwhich the first fluid, in this instance a heat-transfer fluid,circulates. Said heat-transfer fluid is, for example, glycol water, inparticular when the exchanger 1 acts as a radiator for cooling acombustion engine.

Said tubes 3 are, for example of circular, oval or oblong cross section.In this last instance, their cross section could exhibit concave zonesto give the tubes a reduced bore section in their middle zone. Saidtubes 3 are, for example, made of a metal alloy such as an aluminumalloy. They are notably obtained by electric arc welding.

Said core bundle may further comprise cooling or heat sink fins 4,through which the tubes 3 pass. These tubes are, for example, aligned inparallel in one or more banks and the fins 4, which are providedparallel to one another, are arranged transversely, particularlyperpendicularly, to said tubes 3. To simplify the drawing, only alimited number of fins of the core bundle have been depicted.

The fins 4 are provided with tube passage orifices of a shapecorresponding to the cross section of said tubes. They may also havelouvers to disrupt the flow of the second fluid, namely in this instancean incident air stream. This then encourages the exchange of heatbetween said air stream, flowing between the fins 4, and theheat-transfer fluid circulating through the tubes 3. Said fins 4 areseparated from one another by a spacing which is advantageouslyconstant.

Said exchanger additionally comprises two end header tanks 2 spacedapart parallel to one another and connected by the tubes 3. Said tubes 3and said tanks 2 allow said first fluid to circulate between them. Forpreference, the dimensions of the fins 4, in plan, correspondsubstantially to those of the header tanks 2, for the sake of thecompactness of the heat exchanger 1.

In the case of an application as a cooling radiator cooling a motorvehicle engine, the heat-transfer fluid coming from the tubes andpassing through one of the header tanks is conveyed, by a feed pipe, tothe various hot parts of the engine (the engine block, cylinder head,etc.) that need cooling before being returned, now heated, by a returnpipe to the other header tank of the radiator to circulate once againthrough the tubes. The exchange of heat between the hot heat-transferfluid circulating through the tubes of the exchanger and the stream ofair passing between said tubes in order to lower the temperature of theheat-transfer fluid, is encouraged by the presence of the fins of whichthe shape, number and material are chosen to optimize the removal of asignificant amount of heat with a view to gradually bringing theheat-transfer fluid passing through the exchanger down to a range oftemperatures that is acceptable and effective for cooling the engine.The fluid feed and return couplings provided in the respective tanksleading to the engine and returning therefrom have not been depicted.

Said tanks 2 comprise a collector plate 6 equipped with orifices for thepassage of said tubes 3. Said tanks 2 further comprise here a cover 8,attached to said collector plate 6. Said cover 8 is, for example, madeof plastic. This is notably polyamide, particularly PA-6,6.

As is best visible in FIG. 2, said cover 8 may have reinforcing ribs 10.It may also incorporate one or more flanges 12 for the fixing of theexchanger, these here being situated at its longitudinal ends, and/orone or more inlet and/or outlet manifolds 14 for the first fluid, inthis instance situated between its longitudinal ends.

According to the invention, said collector plate is made of plastic,notably polyamide, particularly PA-6,6. Such a choice of material makesit possible to limit the effects of corrosion.

FIG. 2 depicts the cover 8 and the collector plate 6 separately. Saidcover 8 and said collector plate 6 may advantageously be fixed togetherby welding, notably using vibration, ultrasound, infrared, laserwelding, hot fusion bonding or the like.

As illustrated in FIG. 3, said exchanger further comprises a retainingplate 16 for holding said tubes 3. Here it is provided with such aretaining plate 16 near each longitudinal end of said tubes 3. Saidplate 16 is, for example, pierced with through-orifices 18 in which thetubes 3 are held. In other words, said tubes 3 and said retaining plate16 are secured to one another, preferably indissociably. Said plate 16is, for example, made of metal. Here it is of substantially rectangularshape.

It should particularly be noted that said retaining plate 16 isdifferent from the fins 4. In particular, it is stronger than theselatter, notably through the choice of a different material and/or adifferent thickness of material.

FIG. 4 depicts the assembly of the exchanger core bundle with the tank2, in the direction of the arrow referenced 20.

As illustrated in the next figures, on completion of this assembly eachretaining plate 16 is fixed to one of the tanks 2. That immobilizes thetubes 3 with respect to the tanks 2. In this instance, said retainingplates 16 are attached externally to said tanks 2 and, moreparticularly, to said collector plates 6.

In order to ensure a good seal between the tanks 2 and the tubes 3, thelatter are advantageously force-fitted into said collector plate 6. Toimprove this result still further and as is more visible in FIG. 4, saidexchanger may comprise a gasket 22, notably an elastomeric gasket,through which said tubes 3 pass.

Said gasket 22 for that reason advantageously has tube passage orifices24. Said gasket 22 here has a flat part connecting annular parts, whichare substantially projecting, forming cuffs or nipples 26 at which saidorifices 24 for the passage of the tubes through the gasket 22 aredefined. In other words, each of said tubes 3 passes through one of saidcuffs 26. Said gasket 22 in this instance is situated outside saidheader tank 2.

Said gasket 22 is compressed between said tubes 3 and said collectorplate 6, at a contour of said orifices 24 provided in said collectorplate 6 for the passage of said tubes 3. In other words, the cuffs 26are compressed here, in line with said collector plate 6, between thetubes 3 and a contour of the orifices for the passage of said tubes 3which are formed in said collector plate 6. Put in yet another way, apart of the cuffs 26 is inserted into said orifices for the passage ofthe tubes 3 which are formed in the collector plate 6, or even extendsaxially as far as the inside of the header tank 2.

Said tubes 3 are advantageously flared 28 at their longitudinal ends.Said flare 28 extends at least facing said retaining plate 16, saidgasket 22 and said collector plate 6. Such a flare 28 encouragesretention of the tubes 3 in said retaining plate 16, forcible fittingthereof into the collector plate 6 and compression of the gasket 22between said tubes 3 and the collector plate 6.

As illustrated in FIGS. 5 and 6, said retaining plate 16 is removable inrelation to said header tank 2.

In FIG. 5, said retaining plate 16 is secured to the collector plate 6by lugs 30 provided on said collector plate 6 and slots 32 provided onsaid retaining plate 16, said lugs 30 clipping into said slots 32.

In FIG. 6, said retaining plate 16 is secured to the collector plate 6by crimping. For that, said collector plate 6 is provided with housings34, in this instance uniformly distributed along its periphery, at thelevel of which crimping teeth 36 of the retaining plate 16 are situated.

A method of manufacturing an exchanger as described above is describedhereinafter.

According to the invention, said tubes 3 are fixed on said retainingplate 16, for example by flaring the end of said tubes.

A prior step of fixing the fins 4 may take place, likewise by flaring.To do that, an expansion olive may be passed along, deforming the tubesto a diameter slightly greater than that of the orifices provided in thefins 4 for passage of said tubes. The flaring of the end of the tubesthen takes place in a second stage, to an even greater diameter.

Furthermore, said header tank 2 is assembled, notably by welding thecollector plate 6 and the cover 8.

In a later step, said retaining plate 16 and, therefore, the heatexchange core bundle, is attached to said header tank 2, notably usingsaid lugs 30 and/or by crimping.

Before that, said tubes 3 will advantageously have been introduced intosaid collector plate 6, notably by force-fitting said tubes 3 into saidcollector plate 6, thereby compressing the gasket 22.

1. A heat exchanger, notably for a motor vehicle, said exchangercomprising: a core bundle for the exchange of heat between a first and asecond fluid, said core bundle comprising a plurality of tubes and aheader tank, said tubes and said tank allowing said first fluid tocirculate between them; and a retaining plate for holding said pluralityof tubes, said retaining plate being fixed to said tank, said tankcomprising a collector plate provided with orifices through which saidtubes pass, and said collector plate being made of plastic.
 2. Theexchanger as claimed in claim 1, wherein said retaining plate isattached externally to said tank.
 3. The exchanger as claimed in claim1, wherein said retaining plate is attached to said collector plate. 4.The exchanger as claimed in claim 1, wherein said tank comprises acover, attached to said collector plate.
 5. The exchanger as claimed inclaim 4, wherein said cover is made of plastic.
 6. The exchanger asclaimed in claim 4, wherein said cover and said collector plate arefixed by welding.
 7. The exchanger as claimed in claim 1, furthercomprising a gasket through which said tubes pass.
 8. The exchanger asclaimed in claim 7, wherein said gasket is situated outside said headertank.
 9. The exchanger as claimed in claim 7, wherein said gasket iscompressed between said tubes and said collector plate (6) at an outlineof said orifices provided in said collector plate for the passage ofsaid tubes.
 10. The exchanger as claimed in claim 1, wherein said tubesare flared at their ends, said flare extending at least facing saidretaining plate and/or said collector plate.
 11. The exchanger asclaimed in claim 1, wherein said retaining plate is removable withrespect to said header tank.
 12. A method of manufacturing an exchangeras claimed in claim 1, said method comprising: fixing said tubes to saidretaining plate; and attaching said retaining plate to said header tank.13. The method as claimed in claim 12, wherein fixing the tubes in theretaining plate comprises flaring said tubes in said retaining plate.14. The method as claimed in claim 12, further comprising: introducingsaid tubes into said collector plate, after fixing said tubes to saidretaining plate and/or before attaching said retaining plate to saidheader tank.
 15. The method as claimed in claim 14, wherein introducingsaid tubes into said collector plate comprises force-fitting said tubesinto said collector plate.